Means for grinding automotive brake shoes



Oct. 30, 1962 H. B. BARRETT 3,060,649

MEANS FOR GRINDING AUTOMOTIVE BRAKE SHOES Original Filed Dec. 12, 1956 2 Sheets-Sheet 1 INVENTOR.

HARRY B. BARRETT ATTORNEY Oct. 30, 1962 H. B. BARRETT 3,060,649

MEANS FOR GRINDING AUTOMOTIVE BRAKE SHOES Original Filed Dec. 12, 1956 2 Sheets-Sheet 2 INVENTOR.

HARRY B. BARRETT ATTORNEY Walla?! States This invention relates to certain new and useful improvements in means for grinding automotive brake shoes and is a division of my copending application Serial No. 627,895, filed December 12, 1 956, which issued as Patent No. 2,960,807, dated November 22, 1960.

Automotive brakes have created a serious brake servicing problem. As is well known, automatic automotive transmissions impose severe wear and tear on automotive brake systems and such transmissions are now very generally used even in the so-called low-priced car field. Consequently, more frequent servicing and repair of automotive brakes becomes necessary. Furthermore, present day types of brake systems require concentric grinding while the shoes are mounted in operating position on the backing plate, inasmuch as such procedure becomes the only practical method of shoe centralization. However, the current widespread adoption and use of full floating shoes makes such brake shoe grinding very difiicult for the reason that both brake shoes are aligned on a common pivot point called the shot anchor and are attached at the opposite ends with an expanding adjuster for wear. The shoes tend to shift diametrally as a unit when grinding or adjusting pressure is applied to either single shoe.

It is, therefore, the primary object of the present invention to provide means for concentrically grinding automotive brake shoes of the full floating type while the latter are mounted in operative position upon the backing plate of the brake.

It is a further object of the present invention to provide means for stabilizing or holding the brake shoe assembly of full floating shoes, while one shoe is being ground so that the shoe being ground will be properly positioned and will thereby be ground to a proper concentric arc.

It is another object of the present invention to provide means for grinding automotive brake shoes of the full floating type so that the braking surfaces of such shoes are precisely concentric quickly, simply, and conveniently, and in a manner which can be employed by the average automotive mechanic with very simple training or instruction.

With the above and other objects in View, my invention resides in the novel features of form, construction, arrangement, and combination of parts presently described and pointed out in the claims.

In the accompanying drawings (two sheets)- FIG. 1 is a diagrammatic view of an automotive brake having so-called full floating shoes;

FIG. 2 is a perspective view of an automobile brake assembly showing the installation thereon of a brake shoe grinder, said grinder being shown on the front spindle of an automobile, constructed in accordance with and embodying the present invention;

FIG. 3 is a perspective view of the brake shoe positioner forming a part of the present invention;

FIGS. 4 and 5 are side elevational views of the brake shoe positioner as respectively applied to two different types of backing plates currently in use;

FIG. 6 is a side elevational view, partly broken away and in section, of a brake'shoe grinder constructed in accordance with and embodying the present invention;

FIG. 7 is a front elevational view of the brake shoe grinder;

atent 3,060,649 Patented Oct. 30, 1962 FIG. 8 is a fragmentary sectional view taken along line 8-8 of FIG. 6;

FIG. 9 is a perspective view of a shim forming a part of the present invention; and

FIGS. 10 and 11 are comparative diagrammatic views of the brake shoe grinder, illustrating the manner of adjustment thereof in relation to various brakes having different dimensional relationships.

In order to understand the present invention, it perhaps should be pointed out that an automotive brake having so-called full floating brake shoes is a brake which comprises a backing plate b, as shown in FIG. 1, and two arcuate brake shoes .3 mounted thereon in such a manner that the shoes s will shift as a unit in a diametral or crosswise direction as indicated by the arrow depending upon the direction in which external force is applied. The specific construction of such automotive brakes, however, is conventional and, therefore, need not be described in particular detail herein. The present invention, broadly speaking, resides in providing a simple and effective method for servicing such brakes by holding one shoe stationary and thereby locating the other shoe in proper position so that its braking surface can be concentrically ground. Such other shoe is then concentrically ground by a grinding tool operatively mounted on the axle spindle or axle. Thereupon, the ground shoe is held stationary so as to position the first shoe and the braking surface of that shoe similarly ground in turn. The present invention also includes the provision of novel shoe positioning and shoe grinding means for carrying out such method.

Referring now in more detail and by reference characters to the drawings, which illustrate practical embodiments of the present invention, A designates a brake shoe grinder somewhat similar to that brake shoe grinder described in the above-mentioned copending application, and comprising a spindle-mounted bracket 1 integrally including a sleeve 2, an abutment plate 3, and a shoulder plate 4 connected by a reinforcing web 5. The abutment plate 3 and shoulder plate 4 are respectively provided with precisely machined outwardly presented contact faces 6, 7, which are relatively perpendicular. Furthermore, the contact face 7 is parallel to the longitudinal axis of the sleeve 2, the latter being providedat oneend with a tapered counter-bore 8, whichis adapted to receive either a conventional wheel bearing or a conical adapter 9, by which the sleeve 2 can be fitted upon a conventional tapered front axle spindle r.

The abutment plate 3 is preferably somewhat triangular in peripheral contour and is provided with three apertures 10, 11, 12, all of which are located at equal radial distances outwardly from the longitudinal center line of the sleeve 2 andare sized for snug-fitting, but slidable, disposition over the axle mounting studs of an automobile rear wheel, the latter being conventional and, hence, not being shown. f

Mounted rigidly in, and extending outwardly from, the shoulder plate 4 is a grinder-frame supporting post 13 having its longitudinal axis perpendicular to the contact face 7 of the shoulder plate 4 and being provided intermediate its ends with a peripheral groove 14 having a tapered face 15. j

Rotatably mounted on the post 13 by means of an integrally formed collar 16 is a radially outwardly projecting frame 17 integrally including an offset arm 18 having an internal passage or air duct 19 terminating in a collarfitting 20. The collar 16 is drilled and tapped to receive a retainer screw 21 having a tapered end 22 for engage ment in the groove 14 and being provided on its outer end with a diametral handle 23. Removably mounted upon the collar-fitting 20 is a filter-canister 24 having a perforated side wall 25 and perforated end wall 26. The can- 3 ister 24 is filled with a suitable filter medium 27. Formed integrally with and extending upwardly from the frame 17 is a motor-supporting bracket 28 including a mounting pad 29 and handle-grip 30. Also provided for optional use upon the post 13 between the collar 16 and the contact face 7 are U-shaped shims 31. These shims 31 can be provided in varying thickness and afford a means of varying the radial distance between the frame 17 and the longitudinal axis of the sleeve 2, the matching tapers of the groove 14 and retainer screw 21 being such as to permit the collar 16 to be locked to the post 13 in various positions of axial adjustment within adequate limits to accommodate various shims 31 of different thicknesses.

Bolted or otherwise rigidly secured upon the mounting pad 29 is an electric grinder 32 having a conventional electrical connector cord 33, switch 34, and grinder shaft 35, the latter being removably provided with a disk-shaped grinder plate 36 having an abrasive disk 37 adhesively or otherwise suitably secured to its exposed face.

As will be noted from FIG. 6, the axis of the shaft 35 is parallel to, but laterally offset from, the axis of the Post 13. Furthermore, the collar 16 is rotatable upon the post 13 when the retainer screw 21 is disengaged from the groove 14. Thus, the frame 17, together with the grinder 32 and related structure can be swung around to various positions of adjustment as diagrammatically shown in FIGS. and 11. By this means, the inner edge of the grinder plate 36 can be located, for instance, at the distance x from the backing plate b with an axial post-toshaft displacement as shown in FIG. 10. Similarly, for a brake of somewhat different dimension or design, the grinder plate 36 can be located at a distance x from the backing plate b with an axial post-to-shaft displacement of y as shown in FIG. 11.

Provided for use in practicing the method of the present invention is a somewhat L-shaped shoe positioning clamp B comprising a side leg 38 and a top leg 39, the latter being integrally provided at its outer end with an extension 40 and an inwardly turned hook-flange 41. Threadedly mounted in, and extending through, the lower end of the side leg 38 is an adjustment screw 42 having a knurled knob 43 at its outer end and a rounded-off contact face 44 on its inner end. Similarly mounted in the side leg 38 is an adjustment screw 45 having a knurled knob 46 at its outer end and a blunt contact face 47 at its inner end. Also threadedly mounted in, and extending through, the extension 40 is an adjustment screw 48 having a knurled knob 49 at its outer end and a blunt contact face 50 at its inner end. Mounted encirclingly around the adjustment screw 48 between the knob 49 and the extension 40 is a spring 51. The side leg 38 is also provided with an internally threaded alternate aperture 52 into which the adjustment screw 45 can also be optionally inserted.

The shoe positioning clamp B is fastened upon the backing plate b and clamped upon the peripheral flange f thereof, substantially as shown in FIG. 4, and the screw 48 adjusted to bear against the brake shoe s and hold it stationary in a selected position so that the opposite shoe s is also positioned in precise relation to the center line of the brake assembly and can be accurately ground. In the case of a brake of somewhat different design wherein the backing plate b does not have a peripheral flange the adjustment screw 45 can be inserted in the alternate aperture 52 and the clamp B thereby firmly attached as shown in FIG. 5.

In use, the brake shoe grinder A may be mounted upon the axle spindles of a front wheel assembly, substantially in the manner shown in FIG. 2, in which case the frame 17 will be positioned on the post 13 in relation to the mounting bracket 1, so that the abutment plate 3 will be faced outwardly, as shown. If the brake lining is to be ground to the so-called normal size, none of the shims 31 need be used and the set screw or retainer screw 21 may then be tightened down so that the frame 17 will be locked securely in such position. If, however, the brake shoe is to be ground several thousandths oversize, one or more shims 31 may be slipped over the post 13 between the contact face 7 and the collar 16 so as to shift the frame 17 toward or away from the contact face 7 by the required amount. When the desired adjustment has been thus effected, the retainer screw 21 is tightened down to hold the frame 17 rigidly in such adjusted position.

Similarly, the grinder A may be mounted on a rear axle assembly substantially in the manner shown and described in detail in connection with the somewhat similar brake shoe grinder forming the subject-matter of my copending application above-mentioned.

Thereupon, the electrical connector cord 33 can be plugged into any conventional source of electrical current and the switch 34 closed to energize the grinder and ro tate the grinder plate 36. With the grinder plate 36 rotating, the frame 17 is swung to-and-fro in a circumferential arc to grind a truly concentric surface upon the braking surfaces of the brake shoes.

After the shoe s has been properly ground, the shoe positioning clamp B is removed and remounted to hold the shoe s and leave the shoe s in position to be ground. When this adjustment has been made, the shoe s may be ground in the same manner and precisely to the same concentric arc. Finally, the positioning clamp B is removed and the brake reassembled for use. In this connection it should be noted that the positioning clamp B is of such size and shape that the drum cannot be reinstalled until the clamp is removed, thereby making it impossible for the mechanic to inadvertently leave the clamp in the brake assembly.

It should be understood that changes and modifications in the means for grinding automotive brake shoes hereinabove set forth may be made and substituted for those herein specifically shown and described without departing from the nature and principle of my invention.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

l. A brake grinder comprising a sleeve adapted for rotative engagement upon an axle spindle of an automobile wheel assembly, a radial web member forming a part of said sleeve and having a shoulder which is laterally offset with respect to the longitudinal axis of the sleeve, a grinder frame pivotally mounted on said shoulder and being pivotable to various positions of adjustment, means for locking said frame in any of said adjusted positions, and grinder means mounted on the outer end of the frame and offset from the pivotal mounting on the shoulder whereby said grinder means may be adjustably positioned toward and away from said wheel assembly incident to pivotal movement of said frame on said shoulder.

2. A brake grinder comprising a sleeve adapted for rotative engagement upon an axle spindle of an automobile wheel assembly, a radial web member forming a part of said sleeve and having a fiat shoulder which is laterally offset with respect to the longitudinal axis of the sleeve, a radial post projecting outwardly from said shoulder, a grinder frame swivelly mounted on said post, means for optionally locking the frame in any selected position on the post, and grinder means mounted on the outer end of the frame and offset from the axis of said post whereby said grinder means may be adjustably positioned toward and away from said wheel assembly incident to swivelling movement of said frame on said post.

3. A brake grinder comprising a sleeve adapted for rotative engagement upon an axle spindle, a radial web member forming a part of said sleeve and having a shoulder which is laterally offset with respect to the longitudinal axis of the sleeve, a post mounted on said shoulder, a grinder frame slidably mounted on said post, a shim removably interposable between the shoulder and the grinder frame for establishing the radial distance be tween the grinder frame and the longitudinal axis of the sleeve, means for locking the frame to the post and for locking the shim between the shoulder and the frame,

and grinder means mounted on the outer end of the frame.

4. A brake grinder comprising a sleeve adapted for rotative engagement upon an axle spindle, a radial web member forming a part of said sleeve and having a shoulder which is laterally offset with respect to the longitudinal axis of the sleeve, a grinder frame operatively mounted on said shoulder, means slidably interposable between the shoulder and the grinder frame for establishing the radial distance between the grinder frame and the longitudinal axis of the sleeve, means operable to tightly secure said slidably interposable means between the shoulder and the frame, and grinder means mounted on the outer end of the frame.

5. A brake grinder comprising grinder-mounting means including a sleeve adapted for rotative disposition in operative relation upon a car-mounted brake assembly, an abutment plate mounted on said sleeve, said abutment plate having an outwardly presented contact face that is perpendicular to the longitudinal axis of said sleeve, said sleeve having a tapered counter bore at one end, said abutment plate also being provided with a plurality of apertures in said contact face, a support-element carried by and projecting radially from the sleeve and having an axis at right angles to the axis of the sleeve, a frame mounted upon the support-element and projecting outwardly therefrom, said frame being rotatable about the axis of the support element, a grinder mounted on the outer end of the frame in laterally offset relation to the support-element so that as the grinder frame is rotated upon the support-element the grinder will be shifted into various adjusted positions toward and away from the brake assembly, and means for locking the frame in any of said adjusted positions.

6. A brake shoe grinder comprising grinder mounting means including a sleeve adapted for rotative disposition in operative relation upon a car mounted brake assembly, an abutment plate mounted on said sleeve, said abutment plate having an outwardly presented contact face that is perpendicular to the longitudinal axis of said sleeve, said sleeve having a tapered counter bore at one end, said abutment plate also being provided With a plurality of apertures in said contact face, a support element carried by and projecting radially from the sleeve and having an axis at right angles to the axis of the sleeve, a frame mounted upon the support element and projecting outwardly therefrom, said frame being rotatable about the axis of the support element, a grinder mounted on the outer end of the frame in laterally offset relation to the support element so that as the grinder frame is rotated upon the support element the grinder will be shifted into various adjusted positions toward and away from the brake assembly, a drive shaft rotatably mounted on said grinder and extending downwardly therefrom, an abrasive grinder plate mounted on said shaft, said shaft having its longitudinal axis parallel to the longitudinal axis of said support element, means for locating the inner edge of the grinder plate at a distance from a brake shoe backing plate with an axial support to shaft displacement, said last-named means being adapted to proportionally increase the axial shaft to support element displacement as the distance from the grinder plate to the backing plate is decreased, and means for locking the frame in any of said adjusted positions.

7. A brake grinder comprising a sleeve adapted for rotating engagement upon an axle spindle of an auto mobile wheel assembly, a web member connected to and extending radially from said sleeve and having a shoulder With a face lying in a plane which is laterally offset with respect to the longitudinal axis of the sleeve, a post projecting outwardly from said shoulder, a grinder frame including a collar received on said post in sWivelling engagement therewith, a groove in said post having a tapered wall, an element radially insertable into said collar, said element having a bearing surface at its inserted end adapted to bear against said tapered wall to lock the frame in any selected position on the post, and grind ing means mounted on the outer end of the frame and offset from the axis of said post whereby said grinding means may be adjustably positioned toward and away from said Wheel assembly.

References Cited in the file of this patent UNITED STATES PATENTS 2,222,640 Thomason Nov. 26, 1940 2,734,319 Billeter Feb. 14, 1956 2,756,552 Gordon July 31, 1956 2,822,650 Barrett Feb. 11, 1958 2,828,589 Hercik Apr. 1, 1958 

